Author: Greg 450EXC
Posted: 04/09/2007 5:34:34 PM
On my second ride out the bike over heated so i have drained and replaced the coolant.
I have followed the instructions but am wondering if anything needs to be done to the right habd tank to bleed it also, do you remove the plug in it as you fill to allow air to escape etc.
Also, should the bike overheat? we were on tight sandy trails so a bit of work and resonably warm.
I think my radiator cap is buggered because on a ride the following day I lost coolant out the cap very quickly and it was a much cooler day.
Reply by 250f canuck on 04/10/2007 3:11:55 PM
Make sure that the coolant anti-freeze you are using is designed for aluminum block/cylinder engines. Aluminum has different cooling requirements than iron/steel and corrodes differently also.
Is the right hand tank you refer to the overflow tank, or is it the right side radiator? If your bike doesn't have an overflow tank you will have to bleed the radiators. Do this by running the bike for a few minutes then topping up the radiator. Your cap may not be messed up if you didn't bleed the system. More air in the system lowers the pressure of the cooling system, which also keeps the boiling point of the coolant mix low and causes a boil-over. Bleed the system and you should be OK.
If you really don't want to overheat and boil over KTM Hard Parts sells a cooling fan that goes on one of the radiators, but that is mainly for really slow going.
Reply by Greg 450EXC on 04/10/2007 5:43:23 PM
Yes it is the right hand radiator I am refering to, there is no overflow tank, which is a bit annoying seeing as there appears to be an overheating problem with a percentage of the 450 EXC.
I will have to check the fluid, it is Motul brand and is specifically designed for performance motorbike so there should not be a problem.
I have bled the system as per the manual but perhaps there is still air in the head?, I let the drain bolt loose until it appear only coolant was flowing out but there will be no harm in leting it run out longer I guess.
Reply by mikejonker on 04/10/2007 7:21:19 PM
Are you bleeding the coolant until there is no bubbles coming out of the top of the head through the bleeder screw? And also are you making sure that the coolant is approximately 10mm above the top of the fins in the left hand radiator?
Reply by Greg 450EXC on 04/11/2007 06:14:18 AM
The coolant may have been overfull after I replaced it, I have read on here that it will spew out very quickly if that is the case because the pressure builds to quickly when overfull / no room to expand etc.
I have bled at the bleeder screw, it was very hard to tell if there were any bubbles comiong out, there was plenty of coolant coming out so I assumed that the air must be finished, i will bleed for a good 5 - 6 seconds again on the weekend to ensure the head is clear of air.
It may be that it was overfull on the weekends second ride. On the first ride it definately overheated but we were in very tight sandy trails that went up and down hills also, therfore hard work, warm day (30 celcius) slow speed / low air flow. Although it was disappointing that the bike got warm i guess the conditions were tough. When you step off an XR 400, you expect everything to be bullet proof 100% of the time. I'll take the power increase, throttle response and overheating of the KTM over the XR400 anyday.
Reply by Greg 450EXC on 04/11/2007 06:19:59 AM
Unfortuately i spent $180.00 Aus on some very good force radiator guards before I was aware of the overheating problem.
As you can see from the picture, the rear brace goes right where the fan would sit, i don't think the fan will go above it due to the tank.
Also at about $260.00 Aus for the fan, I'm tempted to go to the local bike wrecker and get a small fan off a wrecked road bike etc and mount it with a switch, unless i can buy the KTM on / off thermo switch sepately somewhere?
Reply by Admin on 04/11/2007 08:42:26 AM
You can always get a factory radiator cooling fan kit:
They're less than $100 (USD). KTM part number: 59035041044
Reply by Greg 450EXC on 04/12/2007 03:13:10 AM
In Australia the fan kit is $258.49. Hence my desire to solve the problem without the fan, or buy a cheaper fan.
Reply by Admin on 04/12/2007 08:18:17 AM
If you don't mind fabricating your own, there's a PDF in the Honda Tech section that shows a way to add a ~$13 computer style fan to your radiator. It uses a plain ol' switch instead of thermostatic switch though.
I would replace the radiator cap just to make sure it's not the problem, if you haven't already. The bike was designed to run without overheating so there has to be a problem somewhere. My EXC never overheated, even bogging around in sand on a hot day in Southern California.
Reply by Greg 450EXC on 04/12/2007 6:29:07 PM
I never thought of it that way!, your dead right, the bike was designed to run without overheating so i have replaced the cap and I will re bleed at the head and see how it goes.Originally posted by Admin
I would replace the radiator cap just to make sure it's not the problem, if you haven't already. The bike was designed to run without overheating so there has to be a problem somewhere. My EXC never overheated.
Reply by wilthis on 05/11/2007 05:57:20 AM
Just add a coolant recover tank. Some use a turkey baster or plastic bottle. Just run your overflow hose into it. When the bike overheats, it spits out to the tank and when it cools, it sucks it back in.
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